[Gambas-user] A random sort of listview

[Doriano Blengino]

jbskaggs ha scritto:
>
>>> FOR i = 0 TO ListView1.count - 1 STEP 1
>>>  myArray[i] = i 
>>> NEXT 
>>>
>>> FOR i = ListView1.count - 1 TO 0 STEP -1
>>> a = Int(Rnd(i + 1))
>>> SWAP myArray[i], myArray[a]
>>> PRINT i, a
>>> NEXT 
>>>       
Apart from the problem of missing records, there could be also a 
"randomness" problem in the algorithm... I am really not sure, but it 
seems that certain slots have more chances to be swapped than other - 
myarray[0] can be swapped COUNT times, while myarray[count-1] gets only 
a chance.  I am not sure of what this signifies: it is true that the 
swap affects the values contained in slots, and not the slots 
themselves, but anyway there could be another method. One could also do 
this:

    for i = 0 to 1000   ' arbitrary value, large enough (>100?)
      c1 = int(rnd(listview1.count))
      c2 = int(rnd(listview1.count))
      swap myarray[c1], myarray[c2]
    next

This way, every slot gets the same chances to be swapped; for sufficient 
loops, it should make a good job... perhaps more random than before.
And perhaps, as the algorthm is different, it could solve the problem of 
missing records (which I didn't understand...).

Cheers,

-- 
Doriano Blengino

"Listen twice before you speak.
This is why we have two ears, but only one mouth."